Nebulizer apparatus and method

ABSTRACT

A nebulizer for efficiently and reliably delivering aerosolized fluid to an inhaling patient is disclosed. The nebulizer includes a fluid channel air inlet and fluid channel air inlet valve responsive to either a manual force external of the nebulizer, or a patient&#39;s breathing, to begin the nebulization process. Also provided is a method of providing nebulization including the steps of moving a fluid channel air inlet valve against a fluid channel air inlet so that a negative pressure may build up over the fluid in the fluid channel to draw fluid from the fluid reservoir and begin nebulization during inhalation.

CROSS-REFERENCE

This application is a continuation of U.S. application Ser. No.12/501,748, filed Jul. 13, 2009, pending, which is a continuation ofU.S. application Ser. No. 11/280,938, filed Nov. 15, 2005, now U.S. Pat.No. 7,559,322, which is a continuation of U.S. application Ser. No.10/306,886, filed Nov. 27, 2002, now U.S. Pat. No. 6,994,083, whichclaims the benefit of U.S. Provisional Application No. 60/345,173, filedDec. 21, 2001, wherein the entirety of each of the aforementionedapplications is hereby which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for generatingan aerosol for delivery to a patient. More particularly, the presentinvention relates to a nebulizer configured to generate an aerosol incoordination with a patient's breathing. The present invention is alsowell suited for continuously generating an aerosol independent of apatient's breathing.

BACKGROUND

Medical nebulizers that nebulize a fluid into an aerosol for inhalationby a patient are well-known devices commonly used for the treatment ofcertain conditions and diseases. Nebulizers have applications forconscious, spontaneously-breathing patients and for controlled,ventilated patients. As used in this specification, the term “patient”includes, without limitation, humans and animals.

In nebulizers, a diverter is primarily used to direct a gas across aliquid channel to create a venturi effect causing the liquid to beentrained into the gas stream. The term “diverter”, as used in thisspecification, includes, without limitation, any baffle or impinger. Asa result of the nebulization process described above, the fluid istransformed into an aerosol, that is, the fluid is caused to form smallparticles that are suspended in the air and that have a particle size ina range suitable for the intended therapy. A common therapy isinhalation therapy, whereby a patient inhales a medicated aerosol totreat an ailment, such as asthma.

Important considerations in the design of a nebulizer are the timing anddosage regulation of the aerosolized fluid. In some nebulizer designs, acontinuous stream of pressurized gas entrains the fluid against thediverter to constantly generate an aerosol until the fluid in areservoir is depleted. Continuous nebulization may result in a waste ofaerosol during a patient's exhalation or during a delay betweeninhalation and exhalation. The amount of wasted aerosol may be difficultto quantify and some of the aerosol may be lost to condensation on thenebulizer or mouthpiece during periods of non-inhalation. Nebulizersimplementing a timed or non-continuous nebulization may adversely affectparticle size and density as the nebulization is turned on and off.

Effective and economical nebulizer therapy includes the ability toquickly generate an aerosol within a desired particle size range. Aneffective nebulizer preferably provides these features synchronouslywith the inhalation of the patient. In order to actuate a mechanicalnebulizer, a patient's inhalation effort must overcome certainvariables. Depending on the structural configuration of the nebulizer,these variables may include one or more of the following: the volumetricflow rate of the flowing gas; air leaks in the device; the force exertedby the flowing gas on a moveable diverter; and the friction betweenmoveable parts. The greater the flow rate, air leaks and friction, thegreater the inhalation effort required in order to actuate the device.It is desirable that a nebulizer have adequate sensitivity to quicklyrespond to an inhalation while not adversely restricting the patient'sinhalation.

Nebulizer designs in use today often consist of ten or more separateparts that may require expensive and time consuming manufacturing andassembly techniques. Accordingly, it is also desirable to have anebulizer that is inexpensive to manufacture and assemble.

BRIEF SUMMARY

In order to address the deficiencies in the prior art and provideimproved performance, a nebulizer and method are provided. According toa first aspect of the invention, a nebulizer is provided with a housinghaving an ambient air inlet and a chamber for holding an aerosol. An airoutlet communicates with the chamber for permitting the aerosol to bewithdrawn from the chamber. A fluid orifice is adjacent a pressurizedgas inlet, where the pressurized gas inlet is in communication with thechamber and where the fluid orifice is in communication with a fluidchannel. In one preferred embodiment, the fluid orifice is preferablypositioned at the opposite end of a nozzle cover from a fluid inlet,wherein the fluid inlet is capable of fluid communication with areservoir. A diverter is positioned in the chamber adjacent to thepressurized gas inlet wherein pressurized gas from the pressurized gasoutlet is diverted over the fluid orifice. A fluid channel air inletvalve is movably disposed across a fluid channel air inlet, where thefluid channel air inlet is in communication with the fluid channel andthe fluid orifice.

In one embodiment, the fluid channel air inlet valve may be a flexiblemembrane responsive to inhalation or physical contact to seal the fluidchannel air inlet and permit a negative pressure over fluid in the fluidreservoir to be drawn to the fluid orifice. As used in thisspecification, the term “fluid orifice” means either the fluid inlet orthe fluid outlet and may be used interchangeably with these terms. Thenebulizer may have an actuator piston connected with at least a portionof a nozzle cover to move all or part of the fluid orifice, or all orpart of the fluid pathway between the reservoir of fluid and the fluidorifice. Additionally, the ambient air inlet valve may be used toalleviate inhalation effort after an initial period of inhalation. Thediverter may also be movable relative to the nebulizer housing, butfixedly positioned relative to either the pressurized gas orifice orfluid orifice. In yet other embodiments the fluid channel air inletvalve may be a duck-bill valve or an umbrella valve. The fluid channelair inlet may be integrally formed out of a single piece of materialthat also contains an exhalation valve and an ambient air inlet valvefor the nebulizer. Other embodiments may include a cap, discrete orintegrally formed with the valves via a tether, that is sized to holddown the fluid channel air inlet valve and allow continuousnebulization. A protective, substantially rigid grid may cover one ormore of the valves that allows the valves to function and pass air, butthat protects that valve material from inadvertent abrasion and othercontamination.

According to another aspect of the invention, a method of providing anebulized fluid to a patient includes providing a nebulizer having adiverter fixedly positioned with respect to a pressurized gas orifice ina chamber, a fluid reservoir in communication with the chamber, and afluid channel air inlet valve responsive to a pressure change in thechamber to seal a fluid channel air inlet. Upon inhalation through anair outlet connected to the chamber, the fluid channel air inlet valveseals against the fluid channel air inlet and a negative pressure iscreated over fluid in the fluid channel such that medication is drawnthrough the fluid orifice. Further aspects and advantages of theinvention are discussed below in conjunction with the preferredembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of a nebulizer according to one embodiment ofthe present invention.

FIG. 2 is a cross-sectional view of the nebulizer of FIG. 1.

FIG. 3 is an exploded perspective view of the nebulizer of FIG. 1.

FIG. 4 is an exploded perspective view of the nebulizer of FIG. 1.

FIG. 5 is a cross-sectional view of a first alternative nozzle anddiverter arrangement.

FIG. 6 is a second alternative embodiment of a first alternative nozzleand diverter arrangement.

FIG. 7 is a cross-sectional view of the fluid channel air inlet valve ofthe embodiment of FIGS. 1-4 in a non-nebulizing position.

FIG. 8 is a cross-sectional view of the fluid channel air inlet valve ofFIG. 4 in a nebulizing position.

FIG. 9 is a cross-sectional view of an alternative air inlet and fluidchannel air inlet valve in a non-nebulizing position.

FIG. 10 is a cross-sectional view of the valve of FIG. 9 in a nebulizingposition.

FIG. 11A illustrates a first alternative geometry of a chamber floor foruse in the nebulizer of FIGS. 1-4.

FIG. 11B illustrates a second alternative geometry of a chamber floorfor use in the nebulizer of FIGS. 1-4.

FIG. 12 illustrates a third alternative geometry of a chamber floor foruse in the nebulizer of FIGS. 1-4.

FIG. 13 illustrates a fourth alternative geometry of a chamber floor foruse in the nebulizer of FIGS. 1-4.

FIG. 14A is a cross-sectional view of the nebulizer of FIG. 1illustrating the flow of gas and the position of the valves when thenebulizer is at rest in a non-actuated position.

FIG. 14B is a cross-sectional view of the nozzle system of the nebulizerof FIG. 14A.

FIG. 14C is a partial enlarged view of the nebulizer of FIG. 14A.

FIG. 15A is a cross-sectional view of the nebulizer of FIG. 1illustrating the flow of gas and aerosol and the position of the valvesat the start of inhalation when the nebulizer is actuated.

FIG. 15B is a cross-sectional view of the nozzle system of the nebulizerof FIG. 15A.

FIG. 15C is a partial enlarged view of the nebulizer of FIG. 15A.

FIG. 16 is a cross-sectional view of the nebulizer of FIG. 1illustrating gas and aerosol flow and the position of the valves in afully actuated position.

FIG. 17 is an exploded view of a first alternative embodiment of thenebulizer of FIG. 1.

FIG. 18 is a cross-sectional view of the nebulizer of FIG. 17

FIG. 19 is a side view of the nebulizer of FIG. 17.

FIG. 20 is a magnified view of a portion of the nebulizer of FIG. 18.

FIG. 21 is a side view of a second alternative embodiment of thenebulizer of FIG. 1

FIG. 22 is cross-sectional view of the nebulizer of FIG. 21.

FIG. 23 is a cross-sectional view of an alternative gas orifice anddiverter orientation.

FIG. 24 is a cross-sectional view of a second alternative gas orificeand diverter orientation.

FIG. 25 is an exploded view of an alternative embodiment of thenebulizer of FIG. 22.

FIG. 26 is a cross-sectional view of the assembled nebulizer of FIG. 25.

FIG. 27 is a partial cross-section of the fluid channel air inlet valveduring exhalation.

FIG. 28 is a partial cross-section of the valve of FIG. 27 duringinhalation.

FIG. 29 is a perspective view of an alternative embodiment of thenebulizer of FIGS. 1-4.

FIG. 30 is an exploded view of the nebulizer of FIG. 29.

FIG. 31 is a perspective view of the nebulizer of FIG. 29 with a cappositioned to place the nebulizer in a continuous nebulization mode.

FIG. 32 is a cross-sectional view of the nebulizer of FIG. 29.

FIG. 33 is a perspective view of a valve system suitable for use in thenebulizer of FIG. 29.

FIG. 34 is a cross-sectional side view of the valve system of FIG. 33.

FIG. 35 is a front perspective view of an unassembled nozzle system foruse in the nebulizer of FIG. 29.

FIG. 36 is a rear perspective view of an unassembled nozzle system foruse in the nebulizer of FIG. 29.

FIG. 37 illustrates a breath actuated nebulizer and removable cap forconnecting the breath actuated nebulizer into a continuously nebulizingnebulizer.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

A preferred embodiment of a nebulizer 10 for nebulizing a fluid is shownin FIGS. 1-4. As used in this specification, the term “fluid” includes,without limitation, a fluid comprising a medicine, whether in the formof an emulsion, suspension or solution, that can be nebulized into anaerosol.

The nebulizer includes a housing 12 consisting of a chamber 14 that issuited to receive and hold a fluid. The chamber is preferablysubstantially cylindrical, however any of a number of shapes may beused. The chamber 14 includes an angled bottom portion 16 so that anyfluid in the chamber will be directed toward one region of the bottom ofthe chamber to facilitate removal of all the fluid. In one embodiment,the bottom portion 16 is set at an approximate 45 degree angle in orderto reduce wastage by maximizing the amount of fluid that is evacuatedfrom the chamber for nebulization. An air outlet 18 extends away fromthe housing 12 and communicates with the chamber 14. A barrier 20 on thehousing forces any aerosol generated in the chamber to flow up and overthe barrier 20 before passing through the air outlet 18. The indirectpath formed by the barrier and the air outlet preferably helps to limitthe particle size of the aerosol that escapes the chamber 14.

Preferably, the housing is integrally formed with a lid portion 22 via ahinge 24 such that the lid portion 22 may be sealed and unsealed againstthe top of the housing to allow someone to fill the chamber 14 with afluid. The lid portion 22 of the housing 12 is preferably molded as onepart with the chamber 14.

The lid 22 preferably includes a group of openings suited to receive anair inlet valve 26, an exhalation valve 28 and a fluid channel air inletvalve 30, respectively. A first opening 32 is sized to accommodate theexhalation valve 28, a second opening 34 is sized to accommodate the airinlet valve 26, and the third opening 36 is sized to accommodate thefluid channel air inlet valve 30. The housing and lid may be constructedof a single piece of material formed by an injection molding process.Suitable materials include a plastic material, such as polypropylene,polycarbonate or a polycarbonate blend, or a metal material.

In a preferred embodiment, each of the air inlet valve 26, exhalationvalve 28 and fluid channel air inlet valve 30 is integrally formed intoa valve system 38 from a single piece of flexible material. Theexhalation valve 28 preferably is mounted into the first opening 32 by acenter anchor 33 so that the assembled valve and opening form abutterfly configuration allowing air to escape upon exhalation andsealing upon inhalation to prevent inhalation of air through theopening. The air inlet valve 26 preferably has a duck bill valveconfiguration and is mounted in the second opening 34 of the lid by twoanchors 27 that cooperate with anchor openings 25 on opposite sides ofthe second opening 34. The duck bill configuration is oriented with thetapered portion directed into the chamber 14 so that ambient air may bedrawn in upon inhalation and so that the parallel sealing members, orlips, of the valve prevent any flow of air out of the chamber uponexhalation. An ambient air guide 29 is preferably integrally formed in,or attached to, the lid portion 22. The ambient air guide 29 is disposedunder the second opening 34 and the air inlet valve 26 so that distalopening 35 directs ambient air over the aerosol generating structure.

The fluid channel air inlet valve 30 preferably mounts into the thirdopening 36 and completely seals the third opening. Preferably, the fluidchannel air inlet valve is a flexible membrane having a thickness thatis sensitive to, and flexibly movable in response to, air pressurechanges within the chamber 14 corresponding to inhalation and exhalationthrough the air outlet 18. As explained in greater detail below, thefluid channel air inlet 64 positioned inside the chamber and directlyadjacent to the fluid channel air inlet valve may be sealed and unsealedsynchronously with a patient's breathing or may be manually actuated byphysical contact against the outside of the valve 30. In one embodiment,the material is flexible rubber material. Although individual valves maybe fabricated separately on separate pieces of flexible material, or thevalves may each be constructed from numerous individual components, thevalve system 38 is preferably a one-piece, integrated constructionreducing the part count and cost of manufacturing (including the cost ofassembly).

Referring to FIGS. 3-4, a portion of the chamber wall is cut-out 40 inorder to accommodate the nozzle system 42. The nozzle system 42 isconfigured to allow for frictional or snap fit assembly onto the wall ofthe chamber 12. A pair of guide slots 44 on either side of the cut-out40 cooperate with the edges 46 of the nozzle assembly 42 to provide fora snug, substantially airtight fit. A recessed channel 48 formed in thewall of the chamber 14 directly below the cut-out 40 forms part of thefluid channel 50 (FIG. 2) when the nebulizer 10 is fully assembled.

The nozzle system 42 includes a pressurized gas nozzle 52 that, whenassembled with the housing 12, extends outside the chamber 14 at aproximal end and tapers down to a pressurized gas orifice 54 at a distalend positioned inside the chamber. A nozzle cover 56 and a fluid channelstem 58 are attached to the gas nozzle portion of the nozzle system 42by a living hinge 60 (FIG. 3). When the two parts of the nozzle system42 are closed, the nozzle cover 56 forms a fluid chamber 62 around aportion of the gas nozzle, where the fluid chamber is in fluidcommunication with the fluid channel stem 58 and a fluid channel airinlet 64.

A passageway 55 (FIG. 2) may be formed by a spacing between the gasnozzle 52 and nozzle cover 56, a groove in the inner circumference ofthe nozzle cover, a groove in the outside of the nozzle, or acombination of grooves on the outside of the nozzle and inside of thenozzle cover. The fluid orifice 57 is positioned adjacent thepressurized gas orifice 54. As illustrated in FIGS. 2 and 14C, the fluidorifice is an annular orifice defined by a gap between the innerdiameter of the tip of the nozzle cover and the outer diameter of thetip of the nozzle. In one preferred embodiment, the outer diameter ofthe tip of the nozzle is 2 mm and the inner diameter of the nozzle covertip is 2.46 mm. Other diameters may also be used. Although a singleannular orifice is shown, embodiments where the fluid outlet has othershapes, or comprises more than one discrete orifice positioned adjacentthe pressurized gas orifice, are also contemplated.

In this embodiment, the fluid channel air inlet 64 is located near thetop of the chamber 14 and is substantially parallel to the longitudinalaxis of the chamber 14. The distal end of the nozzle cover forms a fluidorifice such that the fluid and gas orifices 57, 55 are substantiallyparallel to each other. The space between the nozzle cover 56 and thepressurized gas nozzle 52 forms the fluid passageway 55 at the distalend which leads to the fluid orifice 57. A non-moveable diverter 66 islocated adjacent the distal end. The diverter directs the gas across thefluid orifice 57 to create a venturi effect, thereby causing the fluidto be entrained into the gas stream to create an aerosol. Preferably,the diverter 66 is attached to, or integrally molded with, the nozzlecover 56. Alternatively, the diverter may be connected to the inside ofthe nebulizer 10.

As best shown in FIG. 4, a support beam 68 connects the diverter 66 tothe nozzle system 42. Preferably, the diverter 66 has a flat surfacehaving a predetermined area and is positioned at a fixed distance fromthe gas orifice 54. The diameter of the gas orifice may be varied, butis preferably 0.46 mm. In one preferred embodiment, the distance betweenthe diverter and nozzle is in the range of 0.15 mm to 1.25 mm, and mostpreferably 0.75 millimeters (mm), and the width of the diverter isapproximately 4.5 mm. These dimensions may be varied to achieve adesired particle size and aerosolization as is known to those of skillin the art. The surface of the diverter 66 is also preferably alignedparallel to the surface of the distal end of the gas nozzle 52 andperpendicular to the flow of pressurized gas through the gas orifice 54.Other diverter embodiments may also be implemented. For example, FIG. 5illustrates a diverter 70 having a perpendicular surface with a widthless than 4.5 mm. In other embodiments, a diverter 72 with a wedge shapeor other non-perpendicular orientation may be used as shown in FIG. 6.

The fluid channel stem 58 extends substantially vertically along thelongitudinal axis of the chamber 14. The stem has a carved out portion59 which forms an enclosed lumen once it is assembled and mated with therecessed channel 48 in the chamber wall. The resulting fluid channelshape is substantially rectangular. In other embodiments, the recessedchannel 48 and carved-out portion 59 of the fluid channel stem 58 may beconstructed to cooperate and form any of a number of continuous orvarying cross-sections along their lengths. In another embodiment, therecessed channel 48 and fluid channel stem 58 may combine to form aplurality of separate fluid channels. In one preferred embodiment, thechamber has a volume of approximately 50 milliliters (ml), with amaximum fluid fill volume of 5 ml. In this embodiment, the fluid channellength is approximately 22.8 mm.

Referring to FIGS. 1-4, the fluid channel air inlet valve 30 is aflexible membrane that on inhalation substantially seals the fluidchannel air inlet 64 communicating with the fluid inlet tube. Oncesubstantially sealed, the necessary pressure is created inside thehousing in order to entrain the fluid up the fluid channel into the pathof the pressurized gas causing the fluid and gas to mix resulting in anaerosol with the desired particle size characteristics. The flexiblemembrane is preferably very sensitive to flow and, therefore, can betriggered at low flows making the apparatus suitable for children andthe elderly who typically have low rates of inhalation. Further, themembrane can also be manually depressed. Accordingly, the patient or thecaregiver can manually actuate the apparatus.

Referring to FIGS. 7 and 8, in one preferred embodiment the fluidchannel air inlet valve 30 is configured to deflect over a gap G, in therange of 0.5-1.0 mm, and most preferably approximately 0.75 mm, beforeit blocks the end of the fluid channel air inlet 64. Other gap distancesmay be used with variations in the parameters of the membrane, geometryand diameter, and variation in other aspects of the nebulizer such asfluid channel air inlet. FIG. 7 illustrates the spaced apartrelationship that exists during exhalation or at rest, while FIG. 8shows the fluid channel air inlet valve 30 sealing against the fluidchannel air inlet during inhalation. In this embodiment, the fluidchannel air inlet valve is designed to respond to a negative pressure ofapproximately 0.5-1.0 cm H₂O to achieve this deflection. The thicknessof the membrane may be approximately 0.2 mm. The outer diameter D₁ is 14mm, the responsive membrane diameter D₂ is approximately 11 mm and theeffective area of the membrane D₃ is approximately 6.5 mm. As shown, thearea between D₁ and D₂ is used to form a grommet-type connection to holdthe membrane in the opening 36 of the lid portion. The area between D₂and D₃ functions as a rolling diaphragm to allow the membrane to move upand down in response to minimal negative pressure in the chamber. Othergap distances G, and geometries, may be utilized in other embodiments.

In one alternative embodiment, illustrated in FIGS. 9 and 10, acombination ambient air inlet valve and fluid channel air inlet valvemay be used instead of separate ambient air inlet and fluid channel airinlet valves. The combination valve 31 may be constructed of a flat,flexible material that will remain closed during exhalation and at rest(FIG. 9), and flex in response to negative pressure in the chamber, orphysical contact with the valve, to allow ambient air into the nebulizerand to contact and seal against a fluid channel air inlet 64 to initiatenebulization (FIG. 10). Another variation contemplated for thisalternative embodiment is a rigid material connected to the container 12or top portion 22 by a hinge having a biasing member configured tomaintain the combination valve closed during exhalation and at rest,while allowing the combination valve to open at a desired negativepressure and initiate nebulization by sealing against the fluid channelair inlet. Any valve arrangement responsive to a negative pressure andpositioned to seal against a fluid channel air inlet may be used.Additionally, the duck bill valve used as the ambient air inlet valve 26in FIGS. 1-4 may also be designed to open up at a pressure in the rangeof 0.5-1.0 cm H₂O.

Although a flexible membrane and duck bill valve have been shown as thepreferred fluid channel air inlet valve and ambient air inlet valve,these valves may be any type of pressure release valve that would notmove or open until the negative pressure within the nebulizer reaches adesired level, in this example 0.5-1.0 cm H₂O. Additionally, thediameter of the fluid channel air inlet is preferably selected such thatthe negative pressure generated within the fluid channel when thenebulizer is at rest is less than the negative pressure necessary todraw the liquid up through the fluid channel to the liquid orifice. Theexact dimensions necessary for the fluid channel air inlet are dependenton the distance from the nozzle region to the top of the liquid in theliquid reservoir. For example, if the vertical distance from the fluidorifice to the top of the liquid surface in the reservoir is 2 cm, thenthe negative pressure above the fluid in the fluid channel must be lessthan 2 cm H₂O when the nebulizer is in its at rest phase.

In one preferred embodiment, the diameter of the fluid channel air inletis 2.5 mm. In order to adjust the sensitivity of the fluid channel airinlet to a patient's breathing, the fluid channel air inlet valve may beconstructed of a material or material thickness to be more responsive tochanges in air pressure, the spacing between the fluid channel air inletvalve and fluid channel air inlet may be adjusted, and the diameter ofthe fluid channel air inlet may be selected to be of a suitable size tochange the sensitivity. The diameter, thickness, geometry, and durometerof the fluid channel air inlet valve are all factors which may beselected to adjust responsiveness. Preferably, the diameter and positionof the fluid channel air inlet valve is such that a patient or caregivermay also manually actuate the nebulizer by applying pressure to thevalve through physical contact by hand or other object.

Referring to FIGS. 11, 12 and 13, the contour and topology of the bottomof the chamber may also be varied. In FIG. 11A the chamber floor 80 isflat. A concave chamber floor 81 is illustrated in FIG. 11B. A splitangle chamber section 83 connects with a shallow angle section 84 toguide fluid into the steep angle section 83 is shown in FIG. 12. Achamber floor 85 having more than two angled sections is illustrated inFIG. 13.

Referring to FIGS. 14-16, the operation of the nebulizer 10 is describedbelow. The first phase of operation, when the nebulizer is at rest, isillustrated in FIGS. 14A-14C. When the user is passive, such as when theuser is between exhalation or inhalation, or when no user is breathingthrough the air outlet 18, the only flow of air into the chamber 14 isvia the gas nozzle where a source of pressurized gas continuously feedsin gas at a predetermined rate. For example, a gas supply may be set upto supply air at a rate of eight liters per minute. As illustrated bythe flow arrows in FIG. 14A, the pressurized gas exits the gas orifice,impacts the diverter, and flows around the chamber and over the barrier.

After passing over the barrier 20, the air from the pressurized sourceexits through the air outlet and any mouth piece attached to the airoutlet. During the rest phase, the duck bill valve 26 of the ambient airinlet remains sealed and the exhalation valve also remains sealed. Thefluid channel air inlet valve 30, however, remains spaced away from thefluid channel air inlet 64 so that air from within the chamber 14 cancycle through the fluid channel air inlet and between the gas nozzle andnozzle cover out through the fluid orifice 57 as shown in FIG. 14C. Thenegative pressure that would usually be created by the flow of thepressurized gas over the tip of the fluid orifice is eliminated orsignificantly reduced by this configuration. Specifically, because airfrom within the chamber may cycle freely through the fluid channel airinlet and out the fluid orifice, no fluid is drawn up through the fluidchannel because no negative pressure is allowed to form over the fluid.As shown in FIG. 14B, air from within the chamber is drawn through thefluid channel air inlet 64 and into the chamber 62 around a portion ofthe nozzle cover. The air from the chamber 62 then flows through anopening in the bottom of the nozzle cover and out between the nozzlecover and nozzle through the liquid orifice. During the rest phase ofthe nebulizer, no aerosol is being produced and air is simply beingcirculated through the fluid channel air inlet and fluid orifice. Theoverall air pressure inside the nebulizer is slightly positive due tothe continual influx of air through the pressurized gas inlet.

At the start of inhalation, the pressurized gas nozzle 52 continues toinject air at a continuous rate, however now the air pressure inside thenebulizer chamber 14 is slightly negative. As shown in FIGS. 15A-15C,the fluid channel air inlet valve 30 reacts to the start of inhalationby flexing downward onto the opening of the fluid channel air inlet toseal against the fluid channel air inlet 64. Once the fluid channel airinlet is sealed off from air within the chamber, a negative pressureforms in the fluid channel 50 and fluid from the reservoir at the bottom16 of the chamber is drawn up the fluid channel 50 and out to the fluidorifice 57 between the pressurized gas nozzle and the nozzle cover. Asshown in FIG. 15B, the fluid is drawn up between the fluid channel stem58 and the recess 48 in the chamber wall as indicated by the arrow inFIGS. 15B and C. The negative pressure over the fluid is generated bythe flow pressurized gas diverted against the diverter 66 over the fluidorifice 57. When fluid reaches the fluid orifice, it is drawn out andmixes with the pressurized gas to form an aerosol. In this embodiment,aerosolization is enhanced by impacting the fluid/gas mixture againstthe diverter. As shown in FIG. 15A (dotted line indicatingliquid/aerosol and solid line indicating gas) the aerosol is formed andtravels around the diverter and ambient air inlet, over the barrier andout through the air outlet. Until inhalation proceeds to the point wherethe negative pressure generated in the chamber by the inhaling patientis greater than the threshold needed to overcome the force holding thelips of the duck bill valve closed, no ambient air will enter throughthe air inlet. The exhalation valve 28 also remains closed.

As illustrated in FIG. 16, the duck bill valve opens to provide anadditional flow of air into the chamber in response to continuedinhalation. The air from the ambient air inlet is directed over the gasand liquid orifices to enhance mixture and transport of the aerosol. Themembrane of the fluid channel air inlet valve remains sealed over thefluid channel air inlet and liquid continues to be drawn up through thefluid channel and aerosolized in the chamber.

When the patient exhales, the fluid channel air inlet valve 30 respondsto the positive pressure in the chamber to separate from the fluidchannel air inlet and allow air from within the chamber to againcirculate through the fluid channel air inlet in the same manner asshown in FIG. 14B. The duck bill valve 26 seals against the exhalationso that no air exits the ambient air inlet and the exhalation valve 28opens up to permit the patient's exhalation to exit the chamber. Becausethe fluid channel air inlet valve separated from the fluid channel airinlet, no fluid is drawn up through the fluid channel and aerosolizedduring exhalation.

Another preferred embodiment of the nebulizer 110 is illustrated inFIGS. 17-20. In this embodiment, the container 112 is separate from, andthreadably attachable to, the lid 122. A chamber 114 is defined withinthe container between the chamber floor 116 and lid 122. The chamberfloor 116 is preferably curved such that the center of the chamber flooris higher than the perimeter so as to direct any liquid toward theperimeter of the chamber floor. A suction plate 120 integrally connectedwith a nozzle cover 124 is configured to rest directly over the distalend of the pressurized gas nozzle 126 that extends through the chamberfloor. A fluid channel 127 is formed by the spacing between the bottomsurface of the suction plate 120 and the chamber floor, and the spacebetween the pressurized gas nozzle 126 and the nozzle cover 124. In oneembodiment, the suction plate may include one or more small openings toallow passage of fluid from above the suction plate to the fluid channel127.

As in the embodiment of FIG. 1, the nebulizer 110 of FIGS. 17-20includes a fluid channel air inlet 128 in communication with the fluidchannel 127 and a fluid channel air inlet valve 130 to control actuationof the nebulizer. The fluid channel air inlet 128 extends from the sideof the fluid channel 127 toward the distal end of the nozzle cover 124.Preferably, an opening 134 in the side of the chamber 114 adjacent tothe nozzle cover and fluid channel air inlet is sized to receive a fluidchannel air inlet valve 130 flexibly mounted in the opening of thechamber wall. In one embodiment, the fluid channel air inlet valve is arolling membrane snap fit into the opening 134 of the chamber wall. Anair inlet guide 132 is attached to the container 112 and extends fromthe edge of the opening 134 so that the fluid channel air inlet 128 iscentered in the opening 134 when the nebulizer is assembled.

The lid 122 of the nebulizer defines an air outlet 118 that extendsthrough to the inside of the chamber 114 to a chimney structure 136having a diverter 138 positioned on the end. Preferably, the threads forthe lid and container are such that the diverter aligns directly overthe pressurized gas orifice 140 in the chamber. The diverter 138 has acurved surface and is attached to the chimney by several support members142. In operation, the nebulizer receives a continuous flow ofpressurized gas through the gas nozzle and exiting through the gasorifice. At rest, or during exhalation, the fluid channel air inletvalve 130 remains spaced away from the fluid channel air inlet 128 andair inlet guide 132 such that air within the chamber cycles through thefluid channel and out the fluid orifice. Manually, or due to a drop inpressure in the chamber from a patient's inhalation, the fluid channelair inlet valve 130 flexes to cover the proximal end (i.e. the end thatis closest to the membrane) of the fluid channel air inlet guide 132such that the fluid channel air inlet is blocked and a negative pressuregenerated by the flow of pressurized gas over the liquid orificegenerates sufficient negative pressure to draw fluid up the fluidchannel 127. This fluid is then mixed with the pressurized gas anddirected against the diverter 138 to form an aerosol which may be drawnout through the air outlet. A suitable mouthpiece and exhalation valvethat may be adapted to fit to the air outlet 118 are illustrated in U.S.Pat. No. 6,044,841, the entire specification of which is incorporatedherein by reference. Alternatively, a mask with an exhalation valve maybe adapted to fit the air outlet 118. Suitable masks are disclosed inU.S. Pat. Nos. 5,988,160 and 5,645,049, the entire specifications ofwhich are incorporated by reference herein. As is illustrated in FIGS.27 and 28 and described in greater detail below, the membrane used torespond to negative pressure to initiate nebulization may also beconfigured to allow ambient air to flow into the chamber whilemaintaining a seal against the fluid channel air inlet.

FIGS. 21-22 illustrate another embodiment of a nebulizer 210 similar tothe embodiment illustrated in FIGS. 8-11. As shown in FIGS. 21-22, thecontainer of the nebulizer has a pressurized gas inlet 226 that entersinto the chamber 214 at a substantially perpendicular orientation to thefluid channel 227. In this embodiment, the fluid channel 227 is formedin a suction tube 224 attached to the suction plate 220 independently ofthe pressurized gas inlet 226. A fluid channel air inlet extends fromthe suction tube 224 and is oriented to cooperate with a air inlet guide232 connected to the container 212. An opening 234 in the chamber wallreceives the fluid channel air inlet valve 230. Assembled, the fluidchannel air inlet valve 230 and fluid channel air inlet 228 are alignedso that an external force or a negative pressure in the chamber willcause the valve to cover the fluid channel air inlet and allow the fluidin the fluid reservoir on the bottom of the chamber to be drawn up thefluid channel, reach the fluid orifice 236 and mix with pressurized gasentering from the gas orifice 240. Although a separate air inlet valvemay be used, preferably the fluid channel air inlet valve is integratedwith an ambient air inlet valve feature, as described below and shown inFIGS. 27-28, so that the membrane 230 serves a dual purpose.

Also, as illustrated in FIG. 22 the configuration of the gas orifice 240and diverter 238 is such that the diverter 238 is a constricted tubehaving an hour glass-type shape that does not completely block the flowof gas from the gas orifice 240. Instead, the diverter 238 funnels thegas over the fluid orifice 236 so that pressurized gas from thepressurized gas nozzle is channeled over a fluid exit orifice andnebulized as it is drawn into the pressurized gas stream. Thus, unlikethe nozzle and diverter configuration of the embodiment in FIGS. 1-4,the pressurized gas flow is not oriented directly against a diverterstructure which is spaced apart and directly opposes the flow of thepressurized gas to cause the gas to flow substantially perpendicular toits initial path from the gas orifice.

Alternate gas orifice and diverter structures suitable for use in theembodiment of FIGS. 21-22, or in modified embodiments of the nebulizerof FIGS. 1-4, are shown in FIGS. 22-25. In FIG. 23, the liquid orifice250 and suction tube 252 are configured to deflect a portion of thepressurized gas flow and no separate baffle or diverter is used.Similarly, in FIG. 24, the gas orifice 256 for the pressurized gasnozzle is not directly obstructed by the diverter 254. Instead, thepressurized gas orifice 256 is positioned off-center in an asymmetricdiverter cone 258 away from the side of the diverter in which the fluidorifice 260 is formed.

Another embodiment of a nebulizer 310 is illustrated in FIGS. 25 and 26.In this embodiment, the pressurized gas inlet 326 is formed as part ofthe lid 322 in parallel with the air outlet 318. A removable fluidchannel assembly 327 includes a fitting 350 configured to frictionallyfit into the end of the gas inlet 326 extending into the chamber 314. Agas orifice 340 is oriented to direct pressurized gas directly across afluid orifice 336 positioned adjacent to, and perpendicular to, the gasorifice 340.

As with the embodiments of FIGS. 17-22, the nebulizer 310 preferablyutilizes a dual function air inlet valve/fluid channel air inlet valve330. The valve 330 is retained in an opening 334 in the container 312and positioned so that the center of the valve 330 aligns with the fluidchannel air inlet 328 when the nebulizer 310 is assembled. Although thefluid channel assembly 327 is shown having a tube-like structure thatextends to the chamber floor 316, in other embodiments the fluid channelassembly 327 may connect to a suction plate such as discussed above.Also, configurations of fluid and gas orifices other than specificallyshown in FIGS. 25 and 26 may be substituted for the configuration shown.It is contemplated that a diverter may also be used in certainconfigurations of the fluid and gas orifices.

The embodiment of FIGS. 25 and 26 functions substantially similarly tothose of FIGS. 17-22. At rest and upon exhalation, the valve 330 remainsspaced away from the fluid channel air inlet 328 so that gas from thegas orifice cannot create a sufficient negative pressure in the fluidchannel 329 as it passes across the fluid orifice 336 to draw fluid andinitiate nebulization. Upon inhalation, the negative pressure in thechamber draws the valve 330 against the fluid channel air inlet toinitiate nebulization. As inhalation continues, the outer periphery ofthe valve 330 rolls inward toward the chamber and pulls away from theopening 334 so that air inlets 338 are revealed and ambient air flowsinto the chamber.

FIGS. 27-28 illustrate the operation of the air inlet portion of thecombination air inlet/fluid channel air inlet valve 230. As illustratedin FIG. 28, upon inhalation the circumferential inlets 250 on the valve230 adjacent the opening 234 in the chamber wall flex inward to permitpassage of ambient air into the chamber while the center of the valve230 continues to prevent the flow of air into the fluid channel airinlet 228. As shown in FIG. 27, these circumferential inlets 250 resealto prevent passage of air from the chamber to the outside uponexhalation.

FIGS. 29-36 illustrate an alternative embodiment of a nebulizer 410 thatis related to the embodiment of FIGS. 1-4. In this embodiment, thenebulizer 410 includes a lid portion 422 connected by a hinge 424 to thehousing 412. The lid may be repeatedly sealed to allow for a fluid, oradditional fluid, to be placed inside. As in the embodiment of FIGS.1-4, a series of valves 426, 428 and 430 fit into or across respectiveopenings in the lid portion 422 to facilitate operation of the nebulizer410. A substantially rigid grid 419, is configured to attach to the lid422 using a snap-fit or other type of connection mechanism. As shown inFIG. 30, each protrusion 427 on the grid 419 is designed to cooperatewith a receptacle 425 on the lid 422. The grid 419 acts to both securethe various valves 426, 428 and 430 onto the lid 422 and protect thesevalves from abrasion and unintentional contact with fingers or otherobjects. A series of openings on the grid permit the valves 426, 428 and430 captured between the grid and the lid portion freedom to movebetween their respective opened or closed positions as described ingreater detail below. The grid may be constructed of the same materialas the container 412 or any of a number of other substantially rigidmaterials.

The nebulizer of FIGS. 29-36 also includes a cap 433 having an innerdiameter sized to form a friction fit around the annular valve guide439. As will be explained in greater detail below, the cap 433 may beused to manually set the nebulizer to continuously nebulize a fluidpresent in the container 412 by fitting the cap over the annular valveguide 439 in the grid 419 so that the fluid channel air inlet valve 430is held down as is shown in FIG. 32. The nebulizer may be returned toits breath actuated configuration by removing the cap 433 and allowingthe fluid channel air inlet valve 430 to move freely.

An integrally formed valve system 438 that may be used in the nebulizer410 is best shown in FIGS. 30 and 33-34. The valve system 438 mayinclude each of the air inlet valve 426, exhalation valve 428 and fluidchannel air inlet valve, as well as the cap 433 and tether 441, in asingle molded piece. The material used is preferably flexible andresilient. In one embodiment, the material is a flexible rubbermaterial, such as a silicone rubber. Although the individual valves maybe fabricated separately on separate pieces of flexible material, or thevalves may each be constructed from numerous individual components, thevalve system 438 is preferably a one-piece, integrated construction. Thecap 433 is shown as connected to the valve system 438 by a tether 441.The cap 441 may be manufactured with one or more pieces of linkingmaterial 453 between the cap and the main body of the valve system 438so that the cap and tether do not become damaged in shipment or get inthe way with the operation of the nebulizer 400 if the cap will not beused. The linking material 453 may be manufactured with a thin piece ofthe same material used for the rest of the valve system so that it maybe purposefully cut or torn by a user.

The cap and tether may be fabricated separately from the rest of thevalve system or the tether may be eliminated altogether in otherembodiments. A separate cap may be used with this embodiment ofnebulizer 400 to cause continuous nebulization, or with any of a numberof breath actuated nebulizers having externally accessible actuatormechanisms. As shown in FIG. 37, a discrete cap 533 may be sized to fitover the movable indicator/actuator 530 of other breath actuatednebulizers 500, such as those disclosed in U.S. Pat. No. 6,044,841, theentirety of which is incorporated by reference herein. The removable capacts to manually hold down an actuator to turn the normally breathactuated nebulizer into a continuous nebulizer that will continuallynebulize a fluid regardless of whether a patient is inhaling orexhaling. In other embodiments, the cap may be implemented by strap orsleeve sized to both grip the container and fit over the valve or otheractuator that controls nebulization of the nebulizer.

Referring again to FIGS. 29-36, the air inlet valve 426 in FIGS. 29-34is an umbrella valve, unlike the duck-bill valve embodiment of FIGS.1-4. The umbrella valve is preferably manufactured as a single piecewithin the valve system 438. A thin, flexible hood 443 is connected tothe valve seat 445 by spaced apart legs 447. Prior to assembly, the hood443 and legs 447 are extended as shown in FIG. 33. In preparation forassembly, the hood 443 is pressed down into the valve seat 445 leavingthe hood biased close against the valve seat and the legs curled beneathas shown in FIG. 32.

In one embodiment, the hood 443 is 15 millimeters (mm) in diameter withan inner portion extending 11 mm in diameter and having a substantiallyconstant thickness of about 0.25 mm. The outer annular portion 451 ofthe hood has a bump of increased thickness, of about 0.55 mm, in orderto help control deformation of the hood when mounted in the nebulizerand to help reduce noise generated when air is drawn through the valve426. The legs 447 may be about 5 mm thick in this embodiment. It is alsocontemplated that the hood 443 may be constructed from a uniformthickness material or a material that is manufactured to contain avariety of thicknesses. The thickness and diameter of the hood 443, andthe thickness of the legs 447, may be adjusted as necessary to obtainthe desired flexibility and sensitivity to inhaled air. As shown in FIG.32, the air inlet valve 426 covers the opening in the lid portion 422over the ambient air guide 429. The hood 443 is oriented toward theinterior of the container 412 so that the negative pressure resultingfrom inhalation through the air outlet will cause the hood to flex awayfrom the valve seat 445 and allow air into the chamber 414.

The fluid channel air inlet valve 430 differs from that of theembodiment of FIGS. 1-4 in that the flexible membrane of the valve 430carries a centrally located pillar 449 positioned to extendperpendicularly through the surrounding membrane of the valve 430 suchthat one end of the pillar 449 is positioned above the fluid channel airinlet 464 and the other end extends through the annular valve guide 439in the grid 419. The fluid channel air inlet valve is configured todeflect over the gap between the end of the pillar and the opening ofthe fluid air inlet channel, where the gap is preferably in the range of0.5-2.0 mm, and most preferably approximately 1.3 mm, before it blocksthe end of the fluid channel air inlet 464. Other gap distances may beused with variations in the parameters of the membrane, geometry anddiameter, and variation in other aspects of the nebulizer such as thesize of the fluid channel air inlet.

As with the embodiment of FIGS. 1-4, the fluid channel air inlet valve430 is designed to be spaced away from the fluid channel air inletduring exhalation and to cover the fluid channel air inlet during airinhalation so that the negative pressure from the continuous gas flow inthe gas nozzle will draw fluid up the fluid channel for nebulization.Although responsiveness may be tuned for particular applications, in oneembodiment, the fluid channel air inlet valve is designed to respond toa negative pressure of approximately 0.5-1.0 cm H₂O to achieve thedeflection necessary to cover the fluid channel air inlet 464 and allowfluid to be drawn up for nebulization. The exhalation valve 428 may be aflap of material extending from the edge of the valve system 438 that isthin enough to move away from an opening in the lid 422 duringexhalation, and both large enough and rigid enough to seal off thatopening during inhalation.

The nebulizer 400 embodiment of FIGS. 29-36 also differs from that ofFIGS. 1-4 in that a barrier 417 to prevent large droplets from escapingthe nebulizer is disposed on the underside of the lid portion 422adjacent the chimney 429 so that a lower barrier 420 may be used wherethe air outlet 418 meets the wall of the container 412 to furtherimprove air flow through the outlet 418. In addition, as shown in FIGS.35-36, the nozzle system 442 differs from that in FIGS. 1-4 in that thenozzle cover 456 does not extend to the base of the gas nozzle 452 sothat the fluid chamber 462 opens up and provides less restriction tofluid flow from the lumen formed by the combination of the recessedchannel 448 chamber wall and the recessed portion 459 of the fluidchannel stem 458. In alternative embodiments, the wall of the nozzlecover 456 may be fabricated at different heights to vary the amount thatfluid flow is restricted in the chamber 462. Another difference betweenthe nozzle system 442 shown in FIGS. 35-36 and the nozzle system 42shown in FIGS. 1-4 is the configuration of the liquid channel formedbetween the gas nozzle 452 and the nozzle cover 456 that culminates inthe liquid orifice 457 (FIG. 32). Specifically, in the embodiment ofFIGS. 35-36, this liquid channel either widens or maintains a constantcross-section from the liquid orifice 457 towards the base of the gasnozzle 452 at the nebulizer container wall, as compared to thecross-section of the liquid channel defined by the nozzle and nozzlecover shown in FIGS. 1-4 that widens in the middle and narrows again ateach end.

Also, performance of the nebulizer may be adjusted by narrowing orwidening the recessed portion of the fluid channel stem. For example, bynarrowing the recessed portion of the stem, the nebulizer efficiency maybe improved because less fluid is left in the reservoir when thenebulizer begins to sputter out and thus the amount of fluid requiredfor the nebulizer to produce a desired amount of aerosol may be reduced.In one embodiment, the chamber has a volume of approximately 40-45milliliters (ml), with a maximum fluid fill volume of 5 ml. In thisembodiment, the fluid channel length L is preferably in the range of20-45 mm and most preferably approximately 35 mm. Depending on any oneof a number of variables, such as the viscosity of the fluid in thenebulizer, the cross-sectional area of the end of the channel formed bythe recessed portion 459 of the fluid channel stem 458 and the containerwall may be in the range of 1-16 square millimeters. Again, any of theabove dimensions may be adjusted to tune a particular nebulizer for aspecific fluid.

In all of the above-embodiments, a nebulizer capable of both breathactuation and manual actuation has been disclosed where a diverter, gasorifice, and liquid orifice are maintain in a fixed position with oneanother at all times. Nebulization is initiated by movement of a valveover the fluid channel air inlet that is in communication with the fluidchannel linking the liquid orifice with the reservoir in the chamber. Byusing a flexible membrane as the fluid channel air inlet valve, a veryfast and reliable response to both increased and decreased pressureswithin the chamber of the nebulizer may be realized. As illustrated inthe embodiments of FIGS. 1-7 and 29-36, this design may be used tosimplify and reduce the number of components needed to assemble anebulizer. As few as three separate molded assemblies may be snapped fittogether without the need for any separate fasteners. Further, noseparate spring biasing members or any type of metal component isnecessary in the design of a nebulizer according to a preferredembodiment. Additionally, a variety of fluid channel configurations maybe utilized with the fluid channel air inlet and fluid channel air inletvalve design discussed herein. As described above, the fluid channel maybe a separate element from the pressurized gas nozzle or may be formedin cooperation with the pressurized gas nozzle. Similarly, the fluidchannel may be contained in a single component of the nebulizer orformed from the mating of more than one assembly in the nebulizer.

It is intended that the foregoing detailed description be regarded asillustrative rather than limiting, and that it be understood that thefollowing claims, including all equivalents, are intended to define thescope of this invention.

We claim:
 1. A nebulizer for generating an aerosol, the nebulizercomprising: a housing having an air inlet and a chamber for holding theaerosol; an air outlet communicating with the chamber for permitting theaerosol to be withdrawn from the chamber; a pressurized gas inletlocated in the chamber; a diverter surface positioned in the chamber ina fixed position relative to the pressurized gas inlet, the divertersurface defining a fluid orifice positioned at a non-parallel angle tothe fluid orifice, wherein the diverter surface is positioned to divertgas issuing from the pressurized gas inlet over the fluid orificedefined by diverter surface; a fluid channel in communication with thefluid orifice; a fluid channel air inlet in communication with the fluidchannel; and a fluid channel air inlet valve movably positioned adjacentthe fluid channel air inlet, wherein the fluid channel air inlet valveis moveable in response to a patient's breathing between a nebulizingposition, where the fluid channel air inlet valve seals against thefluid channel air inlet to permit a negative pressure to draw a fluidthrough the fluid channel, and a non-nebulizing position, wherein thefluid channel air inlet valve is configured to permit air to enter thefluid channel air inlet so as to prevent formation of a negativepressure sufficient to draw the fluid through the fluid channel.
 2. Theapparatus of claim 1, wherein the fluid channel air inlet valve ispositioned in the housing such that a first side of the valve is incontact with ambient air outside the chamber and a second side of thevalve is in contact with a body of air inside the chamber, the fluidchannel air inlet valve positioned to actuate the nebulizer in responseto a physical contact received on the first side of the valve.
 3. Theapparatus of claim 1, wherein the diverter surface comprises a curvedsurface having a proximal sloped portion facing toward the pressurizedgas inlet, a distal sloped portion facing away from the pressurized gasinlet, and a raised peak portion between the proximal and distal slopedportions.
 4. The apparatus of claim 3, wherein the diverter surface is acontinuously curved surface.
 5. The apparatus of claim 4, wherein alongitudinal axis of the fluid orifice is oriented substantiallyperpendicular to a longitudinal axis of the pressurized gas inlet. 6.The apparatus of claim 3, wherein the fluid orifice is off-center fromthe raised peak portion.
 7. The apparatus of claim 6, wherein the fluidorifice is positioned between the raised peak portion and the distalsloped portion of the diverter surface.
 8. The apparatus of claim 7,wherein the pressurized gas inlet is positioned over the divertersurface between the proximal sloped portion and the raised peak portion.9. A nebulizer for generating an aerosol, the nebulizer comprising: ahousing having an air inlet and a chamber for holding the aerosol; anair outlet communicating with the chamber for permitting the aerosol tobe withdrawn from the chamber; a pressurized gas inlet located in thechamber; a constricted tubular segment located in the chamber, theconstricted tubular segment having two open ends each with a diametergreater than a diameter of a middle portion positioned between the twoopen ends, wherein the pressurized gas inlet is surrounded by a first ofthe two open ends and oriented toward a second of the two open ends;wherein an interior surface of the constricted tube segment comprises adiverter surface and the diverter surface defines a fluid orifice;wherein the diverter surface is positioned to divert gas issuing fromthe pressurized gas inlet over the fluid orifice defined by divertersurface; a fluid channel in communication with the fluid orifice; afluid channel air inlet in communication with the fluid channel; and afluid channel air inlet valve movably positioned adjacent the fluidchannel air inlet, wherein the fluid channel air inlet valve is moveablein response to a patient's breathing between a nebulizing position,where the fluid channel air inlet valve seals against the fluid channelair inlet to permit a negative pressure to draw a fluid through thefluid channel, and a non-nebulizing position, wherein the fluid channelair inlet valve is configured to permit air to enter the fluid channelair inlet so as to prevent formation of a negative pressure sufficientto draw the fluid through the fluid channel.
 10. The apparatus of claim9, wherein the fluid channel air inlet valve is positioned in thehousing such that a first side of the valve is in contact with ambientair outside the chamber and a second side of the valve is in contactwith a body of air inside the chamber, the fluid channel air inlet valvepositioned to actuate the nebulizer in response to a physical contactreceived on the first side of the valve.
 11. The apparatus of claim 9,wherein the diverter surface comprises a curved surface having aproximal sloped portion facing toward the pressurized gas inlet, adistal sloped portion facing away from the pressurized gas inlet, and araised peak portion between the proximal and distal sloped portion. 12.The apparatus of claim 11, wherein the diverter surface is acontinuously curved surface.
 13. The apparatus of claim 12, wherein alongitudinal axis of the fluid orifice is oriented substantiallyperpendicular to a longitudinal axis of the pressurized gas inlet. 14.The apparatus of claim 11, wherein the fluid orifice is off-center fromthe raised peak portion.
 15. The apparatus of claim 14, wherein thefluid orifice is positioned between the raised peak portion and thedistal sloped portion of the diverter surface.
 16. The apparatus ofclaim 15, wherein the pressurized gas inlet is positioned over thediverter surface between the proximal sloped portion and the raised peakportion.
 17. The apparatus of claim 16, wherein a longitudinal axis ofthe pressurized gas inlet is positioned off-center of a longitudinalaxis of the constricted tubular segment.
 18. A nebulizer for providingan aerosol to an inhaling patient, the nebulizer comprising: a housinghaving an air inlet and a chamber for holding the aerosol; an air outletcommunicating with the chamber for permitting the aerosol to bewithdrawn from the chamber; a pressurized gas inlet located in thechamber; a constricted tubular segment located in the chamber, theconstricted tubular segment having two open ends each with a diametergreater than a diameter of a middle portion positioned between the twoopen ends, wherein the pressurized gas inlet is surrounded by a first ofthe two open ends and oriented toward a second of the two open ends;wherein an interior surface of the constricted tube segment comprises adiverter surface and the diverter surface defines a fluid orifice;wherein the diverter surface is positioned to divert gas issuing fromthe pressurized gas inlet over the fluid orifice defined by divertersurface; a fluid channel in communication with the fluid orifice; afluid channel air inlet in communication with the fluid channel; and afluid channel air inlet valve movably positioned adjacent the fluidchannel air inlet.
 19. The apparatus of claim 18, wherein the divertersurface is in a fixed position relative to the pressurized gas inlet.20. The apparatus of claim 19, wherein: the diverter surface comprises acontinuously curved surface having a proximal sloped portion facingtoward the pressurized gas inlet, a distal sloped portion facing awayfrom the pressurized gas inlet, and a raised peak portion between theproximal and distal sloped portion; and wherein the fluid orifice isoff-center from the raised peak portion.